The present invention relates to an improved moisture detection probe and in particular to a moisture detection probe which utilises a temperature sensor for detection of moisture present in a medium.
The present invention also provides a moisture sensing probe which provides accurate recordal of moisture content in a medium such as soil by measurement of heat loss in a conductor by a temperature sensor contained in, on or near the conductor preferably located at the extremity of the probe. Unlike the prior art moisture detection probes, the present invention is unaffected by those parameters in soils which have previously created inaccuracies when soil moisture is measured by the prior art probes.
The temperature sensor at the extremity of the probe is less sensitive to changes in parameters in the soil environment and in relation to some parameters such as soil pH the performance of the temperature sensor in as much as its ability to generate accurate results is concerned is unaffected.
Although it is feasible for the present invention to be utilised in measuring moisture contents in a number of mediums the present description will be confined to measurement of moisture in a soil medium.
There are presently in existence a variety of probes and detectors for use in the detection of moisture present in a medium such as soil. The prior art probes have been found to be inaccurate due to affectation by a variety of soil parameters such as pH variation, and soil salts.
Among the prior art moisture probes which claim reasonable accuracy there are those which utilise electrolysis to determine the presence of moisture and those which measure the surface tension of the medium in which the moisture is present.
Those probes which utilise electrolysis in order to measure soil moisture content can be seriously affected by change in ionic concentrations and soil salts as electrical conductivity during electrolysis is affected by ionic variation. The variations in ion concentrations cause pre-measurement calibrations to be inaccurate making it difficult to accurately measure moisture content in a particular soil.
These electrolysis probes depend for obtaining readings on electrodes which are placed in the soil. The electrodes are linked to electrical circuitry. The circuit is completed by the presence of moisture in the soil enabling an electrolytic ion transfer to take place. This method for measuring moisture content is inaccurate especially when the moisture content of the soil is low. In addition, variation in acidity or alkalinity of the soil increases or decreases conductivity depending upon which of these phenomena occur. As the readings for moisture content are conductivity dependent, variations in conductivity due to these effects introduce significant error into the moisture content readings.
Moisture probes which rely on measurement of surface tension in soil mediums are generally inaccurate.
Many versions of prior art moisture probes are suitable only as indicators of moisture content. Accuracy is sacrificed because of the effects of the medium variables and due to the inherent deficiencies in the prior art probe mechanisms.